The best chimney draught excluder is one that matches your flue’s shape and measured opening while staying securely in place. These five felt flue plugs cover rectangular, square, and round openings. The 12-inch round Flueblocker is best for a pressure-fit round flue, while the other options suit specific rectangular or square sizes and include telescopic poles. Measure the flue before choosing, and use any plug only when the fireplace is inactive.
| Product | Best for | Specified flue size |
|---|---|---|
| Flue Plug, 8 x 24 Inches | Smaller rectangular flues | 8 x 24 inches or smaller |
| Flue Plug, 13 x 27 Inches | Medium rectangular flues | 13 x 27 inches or smaller |
| Flueblocker, 12-Inch Round | Round flues and pressure-fit installation | 12-inch round or smaller |
| Flue Plug, 13 x 35 Inches | Tall rectangular flues | 13 x 35 inches or smaller |
| Flue Plug, 15 x 15 Inches | Square flues | 15 x 15 inches or smaller |
Flue Plug for 8 x 24-Inch Rectangular Flues
Best for: Homeowners with a smaller rectangular flue measuring up to 8 by 24 inches who want a trimmable felt blocker and an adjustable pole.
The plug measures 9 by 25 inches and has three sewn-in loops to guide trimming. The listing says it can be trimmed for flues measuring 8 by 24 inches or smaller. It is made from fire-resistant felt, which the product description says blocks airflow, drafts, odors, noise, and debris.
A telescopic metal pole adjusts from 16 to 60 inches to help position the plug. This makes it a better fit for buyers who want a pole-assisted setup rather than a simple pressure-fit insert. The listed guidance says the damper should be slightly larger than the flue opening for a secure seal.
Limitation: This model is sized for smaller rectangular openings; do not assume it will suit a larger or differently shaped flue. Measure carefully before trimming, because trimming changes the plug’s dimensions.
Flue Plug for 13 x 27-Inch Rectangular Flues
Best for: Rectangular flues measuring up to 13 by 27 inches, particularly for buyers who want a trimmable felt design with a telescopic positioning pole.
This plug measures 14 by 28 inches and has two sewn-in loops to guide trimming. Its listed fit is for flues measuring 13 by 27 inches or smaller. The fire-resistant felt is described as a barrier against air movement, cold drafts, odors, noise, and debris when the fireplace or wood stove is not in use.
The telescopic metal pole contracts to 16 inches and extends to 60 inches. Compared with the 8-by-24-inch model, this option is better suited to a wider rectangular opening. The product guidance says the damper should be slightly larger than the flue opening to help create a secure seal.
Limitation: The listing gives a rectangular size range, not a universal fit for every flue. Check both dimensions and the shape of your opening before buying or trimming.
Flueblocker for 12-Inch Round Flues
Best for: Buyers with a round flue opening around 12 inches who prefer a pressure-fit plug that does not rely on the fireplace damper mechanism.
The Flueblocker is designed for 12-inch round openings and has an actual diameter of 13 inches for a compression-based fit, according to its product details. It is made from wool and is described as blocking drafts, odors, noise, and falling debris. The plug sits in the flue above the firebox, so the listing says it can be used whether the existing damper is broken, stuck, or missing.
Installation is described as tool-free: press the plug into the opening. The product information also says it can be trimmed with scissors for smaller round openings. It is presented for seasonal or year-round use in inactive fireplaces and wood stoves.
Limitation: This product is designed for round flues, not rectangular or square openings. Confirm the opening’s shape and diameter, and remove the plug before using the fireplace.
Flue Plug for 13 x 35-Inch Rectangular Flues
Best for: Buyers with a taller rectangular flue measuring up to 13 by 35 inches who want a felt plug that can be trimmed to fit.
The plug measures 14 by 36 inches and includes three sewn-in loops to guide trimming. Its listed fit is for openings measuring 13 by 35 inches or smaller. The dense, fire-resistant felt is described as blocking airflow, seasonal drafts, odors, noise, and debris. A telescopic metal pole extends from 16 to 60 inches to assist with positioning.
Choose this model over the 13-by-27-inch option if your measured opening is longer and falls within the stated size range. The product description recommends that the damper be slightly larger than the flue opening for a secure seal.
Limitation: Its larger dimensions do not make it suitable for every flue; the opening must still be rectangular and within the specified measurements. Measure before trimming, and do not leave a plug installed when the fireplace is in use.
Flue Plug for 15 x 15-Inch Square Flues
Best for: Homeowners with a square flue opening measuring up to 15 by 15 inches who want a trimmable felt blocker and telescopic pole.
This model measures 16 by 16 inches and has three sewn-in loops to help guide trimming. The listed fit is for square openings measuring 15 by 15 inches or smaller. Its fire-resistant felt is described as helping to block airflow, cold drafts, odors, noise, and debris when the fireplace is idle.
The included telescopic metal pole adjusts between 16 and 60 inches. That feature may be useful for positioning the plug, while the larger starting dimensions allow some trimming to fit a smaller opening. The product information says the damper should be slightly larger than the flue opening for a secure fit.
Limitation: This is the only listed square option, but it is not a substitute for a round or rectangular plug when the flue has a different shape. Confirm that both sides of the opening are close to the stated square dimensions before selecting it.
Buying Guide: How to Choose a Chimney Draught Excluder
What size flue plug should you buy?
Measure the inside opening of the flue before choosing a product. Record the shape and both dimensions for a rectangular opening, or measure the diameter for a round one. For a square flue, measure both sides. Compare your measurements with the product’s stated maximum fit, not just its product dimensions. The listed felt plugs are larger than their target flue sizes because they are designed to be trimmed or fitted over the opening.
Do not estimate from the fireplace opening or firebox. The flue opening is the relevant measurement. If the flue is irregular, tapered, damaged, or difficult to access, consider asking a qualified chimney professional to identify the correct size and installation point before buying.
Should you choose a round, square, or rectangular design?
Choose a plug shaped for your flue. The Flueblocker is specified for a 12-inch round flue, while the felt models cover 8-by-24-inch, 13-by-27-inch, and 13-by-35-inch rectangular flues, plus a 15-by-15-inch square flue. A product’s ability to be trimmed does not mean it can change shape enough to fit an entirely different opening.
For rectangular options, compare both width and length. Two flues with the same area can have different proportions and may not accept the same plug. For a round option, check diameter rather than circumference or the size of the chimney exterior.
Is a pole or pressure fit better for installation?
The four felt models in this selection include telescopic metal poles that adjust from 16 to 60 inches. Their felt material can be trimmed according to the listed instructions, and the product descriptions refer to positioning the plug with the pole. These features may suit buyers who want help placing a larger mat in the flue.
The Flueblocker uses a different approach: its wool plug is pressed into the round opening for a compression fit and is described as requiring no tools. Consider access to the flue and the plug’s stated installation method. In either case, follow the product instructions and make sure the plug is secure without forcing it into an unsuitable opening.
Can a chimney draught excluder be used while a fire is burning?
These products are described as draft blockers for inactive fireplaces and wood stoves. Do not burn a fire with a plug installed. A flue must be open and unobstructed whenever the fireplace or stove is operating. Remove the plug before lighting a fire, and follow the manufacturer’s safety and use instructions.
The felt products are described as made from fire-resistant material, but that description is not permission to leave one in place during a fire. If the product’s instructions are unclear, do not use it until you have confirmed safe operation with the manufacturer or a qualified chimney professional.
What other features should you compare?
- Material: The rectangular and square options use fire-resistant felt; the round Flueblocker is described as wool.
- Trimming: The felt models have sewn-in loops to guide trimming. The Flueblocker listing says it can be trimmed for smaller round openings.
- Positioning method: Four options include telescopic poles; the Flueblocker is described as a pressure-fit plug.
- Damper condition: The Flueblocker listing says it sits independently of the damper mechanism. The felt plug listings advise that the damper should be slightly larger than the flue opening.
- Seasonal use: The products are intended to block drafts and other airflow through an inactive flue. Check each product’s instructions for storage and maintenance.
How should you check the fit?
Review the product’s dimensions and fit guidance before installation. Trim only as directed, and make gradual cuts so you do not remove more material than needed. A plug that is too small may not stay in place or seal effectively; a plug that is too large may be difficult to position. Do not force a plug into a flue or use it if it cannot be securely and correctly fitted.
After installation, make sure the plug is positioned as instructed and remember that it must be removed before using the fireplace. Keep the removal step in mind when choosing where and how to install it. If you cannot safely reach the flue or verify the fit, seek professional assistance.
Frequently Asked Questions
What is the best draught excluder for a chimney?
The best choice depends on the flue’s shape and measured size. For a 12-inch round flue, the Flueblocker is the round pressure-fit option in this selection. For rectangular or square flues, choose a felt model whose stated dimensions match your opening.
Can I use a chimney plug if the damper is broken?
The Flueblocker listing says it sits in the flue independently of the damper and can be used when the damper is broken, stuck, or missing. Check the instructions for any other plug before relying on it in that situation.
Do chimney draught excluders block odors and debris?
The listed products are described as blocking odors and debris, along with drafts. The Flueblocker also specifically mentions noise and falling debris. The degree of sealing depends on choosing the right size and fitting the product as directed.
Can I trim a chimney flue plug?
The four felt plugs are described as trimmable, with sewn-in loops to guide cuts. The Flueblocker listing also says it can be trimmed for smaller round openings. Follow the specific product instructions and trim gradually.
Should I leave a flue plug in all year?
The Flueblocker listing describes seasonal and year-round use in inactive fireplaces and wood stoves. For other models, follow the manufacturer’s guidance. Remove any plug before operating the fireplace or stove.
How do I know whether my flue is square or rectangular?
Measure the inside opening. If its two sides are approximately equal, it is square; if they differ, it is rectangular. Measure a round opening across its diameter. Use the opening’s shape and measurements to select a compatible plug.